The above-noted articles during their manufacture and also during their further processing must be counted several times. Such counting is easy to perform when such products follow each other in the direction of the delivery with a gap between the adjacent articles, as in such case the counting process may employ a mechanical or electrical sensing device which notes the passing of an article or the absence of it with a "yes" or a "no" pulse, respectively. In the event it is desired at low delivery speed to increase the the number of the delivered articles, then the possibility of stepped or overlapping delivery of the articles can be considered. In the last-mentioned delivery type, however, the counting becomes in most cases considerably difficult. It will not suffice any more a simple "yes" or "no" sensing inasmuch as the gap between the adjacent articles will not be present any more and there will be need to obtain some information as to the fact that an article has passed the counting station and also such information must be made available for the eventual counting itself. Under this condition the jump-like change in the thickness from one article to the other can be considered as a possibility to perform the counting. Such a thickness measuring when the article passes at the measuring station will result in a jump-like indication of the variation which can be used for the counting. In the event one is dealing with thick products then such method appears to be satisfactory. For thin products, especially elastic cuts or paper layers, newspapers, periodicals or notebooks which come in layers and in the case of paper bags or paper sacks, a simple thickness measuring will not suffice or lead to a reliable counting inasmuch as the total thickness of the material which is being delivered in a stepped or overlapping fashion to the measuring station will vary frequently by more than the thickness of an article itself. Therefore the change of the total thickness can not be considered for a reliable counting.
It has been realized that the steps appearing on the upper surface of the stream of articles being delivered in overlapping fashion could be used for the counting and several methods have been proposed and used.
For example, there is a known counting and a sensing arrangement which senses only the height of the step from one to the adjacent article during delivery and employs it for the counting. This operating method has its disadvantage in that the height of the step is relatively small and in order to operate a switching element corresponding large amplification becomes necessary and the small step must be translated into a relatively large operating path. Such condition requires very sensitive mechanical translating elements having a very small play and during the rapid actuation, these become very susceptible to operational defects and, at the same time, under certain conditions they must be set for the height of the jump in the steps. Inaccurate setting in such devices will lead to errors in the counting. In the event of products or articles, such as bags or sacks or thin newspapers, the use of the above devices is totally prohibitive and the result obtained with them, if used, are unsatisfactory. During their operation, the fact that within one article there can be several thicknesses present, such as is the case with bags or sacks having a glued-in bottom in the form of a block or plate bottom, will contribute to additional errors in the counting. Also, in the case of newspapers having several layers, it can be the case that an insert might slip out of its normal position within the article and it can form a more or less defined step despite the fact that the top layer of the newspaper is a single layer. Further defects can be caused by other circumstances, such as when the measuring or sensing station is not pressed or loaded down.
This known operating method further requires that the sensing head itself is not oriented within the sensing station onto the total thickness of the articles passing through in an overlapping stream. It is oriented at a certain distance beyond or ahead of the measuring station so that it can sense the step formed by the articles. This will lead also to further errors in the counting.
The above-noted sensing arrangements are generally characterized by the disadvantage of having short sensing distances and their additional counting errors due to the various thicknesses present in the articles of one product. Therefore, for these arrangements a reliable counting is prohibited.